Method for Transferring Particles

ABSTRACT

Method and apparatus are provided for transferring particles from an upper zone through an intermediate zone to a lower zone. The transfer of particles between the zones through valveless conduits is regulated by varying the pressure of the intermediate zone and the flow rate of gas passing through the valveless conduits. A body within the lower zone is in particle communication with a valveless conduit and obstructs the particle flow within the lower zone.

FIELD OF THE INVENTION

This invention generally relates to the art of solid particle transport.More specifically, the invention relates to methods and apparatus fortransferring particles from an upper zone through a middle zone to alower zone.

BACKGROUND OF THE INVENTION

There are many chemical processes where it is necessary to bring intocontact a fluid and a solid particulate matter, such as adsorbents andcatalysts. Frequently, chemical reactions as well as physical phenomenaoccur for a predetermined period of time in the contact zone, e.g. areaction or adsorption zone. In many of these processes, the particlesare transported between two or more particle containing vessels. Theparticles may be transported for a variety of reasons depending on theprocess. For example, particles may be transported from one contactingvessel or zone into another contacting zone in order to take advantageof different process conditions to improve product yields and/or purity.In another example, particles may be transported from a reaction zoneinto a regeneration zone in order to rejuvenate the particles, and afterrejuvenation, the particles may be transported back to the reactionzone. The particles may be introduced to and withdrawn from the vesselsor zones in a continuous or semi-continuous manner sufficient tomaintain the desired contacting process continuously.

The vessels between which the catalyst is transported are notnecessarily adjacent. The outlet of the source vessel from which thecatalyst is transported may be a significant distance horizontallyand/or vertically from the inlet of the destination vessel to which thecatalyst is transported. Pneumatic conveying through a conduit is a wellknown and commonly used method of transferring catalyst over verticaland horizontal distances. One characteristic of pneumatic conveying isthat because of the pressure difference across the conduit between thesource and destination, the destination pressure must be less than thesource pressure to account for the pressure drop across the pneumaticconveying system. However, process conditions may require thedestination vessel to operate at a higher pressure than this value(source pressure minus pneumatic conveying system pressure drop).Examples include circulating particles between two zones maintained atdifferent pressures; and transferring particles from one vessel toanother where both vessels are maintained at the same pressure. Undersuch conditions, a pneumatic conveying system alone is insufficient totransfer the particles.

A lock hopper is commonly used to transfer particles from a lowerpressure zone to a higher pressure zone. The use of lock hoppers inconjunction with pneumatic conveying is also well known in the art totransfer particles between vessels or zones that are maintained atdifferent pressures. First, a lock hopper transfers particles from theupper, low pressure source zone to a middle zone, and then to a lower,high pressure zone. A pneumatic conveying system then transfers theparticles from the high pressure zone to the destination zone. Althoughthe destination zone has a pressure less than that of the high pressurezone, the destination zone pressure may be greater than that of the lowpressure source. In the art, the term “lock hopper” has been used todesignate the combination of the upper, middle, and lower zones, and“lock hopper” has been used to designate only the middle zone.

In one example, the flow of particles from an upper vessel into themiddle zone and out of the middle zone into a lower zone is controlledby valves located in the conduits or transfer pipes that connect thezones. The valves may be double block-and-bleed ball valves. Thus, abatch of particles may be transferred to the middle zone through theupper valve or valves when the lower valve or valves are closed. Themiddle zone may then be isolated by closing the upper valve(s). Variousconduits may be connected to the isolated volume to introduce or removethe fluid phase, usually gas, or change the pressure inside the middlezone. For example, a regenerated catalyst may enter the vessel, bepurged with nitrogen to remove oxygen, and pressured with hydrogenbefore being transferred to the reactor which is at a higher pressurethan the regenerated catalyst. After catalyst exits the middle zone, themiddle zone can be purged with nitrogen to remove the hydrogen beforefilling again with catalyst.

U.S. Pat. No. 4,576,712 discloses a method and apparatus for maintaininga substantially continuous gas flow through particulate solids in twozones. The solids are moved from a low pressure zone to a high pressurezone by means of a valveless lock hopper system. Maintenance of gas flowwhile simultaneously transferring particles between zones isaccomplished without the use of moving equipment such as valves.

U.S. Pat. No. 4,872,969 discloses a method and apparatus for controllingthe transfer of particles between zones of different pressure usingparticle collection and particle transfer conduits. The solids are movedfrom a low pressure zone to a high pressure zone by means of a valvelesslock hopper system that vents all of the gas from the collection zonesthrough the particle collection conduits. The venting of gas isaccomplished by varying the size of the transfer conduits between zones.

As is known in the art, physical characteristics of the particles andbasic process information such as the operating pressure in the upperand lower zones and the acceptable range of gas flow rates are initialdesign information. Processes are designed from this basic informationand standard particle and gas engineering principles to routinelyprovide stable operating units. Surprisingly, it has been found that aparticular unit will operate predominantly in a stable manner butexperience sporadic upsets. These upsets involving a sudden surge ofparticles from one zone to another, which may reverse the particle flow,have been unpredictable with respect to which unit will be affected, andwhich particle transfer cycle will experience an upset in an affectedunit. These upsets occur despite conformance to the same design methods.Such upsets interrupt the consistent flow of particles and canphysically damage the particles as well as the equipment.

Consequently, there is desire to eliminate these sporadic upsets inorder to minimize damage to the equipment and particles and ensure theconsistent flow of particles. The consistent flow or transfer ofparticles involves a series of steps which can be repeated in a cyclicmanner to transfer the particles in batches. Although it remainsunpredictable whether an upset will occur during any particular cycle inan apparatus, we have discovered that the upsets usually occur duringthe middle zone depressurization step or the middle zone empty step. Ourinvention provides an improved method and apparatus that eliminates allor many of these sporadic upsets without negatively impacting the vastmajority of operating units or cycles that do not experience upsets.

SUMMARY OF THE INVENTION

The invention is a method and apparatus for transferring particles froman upper zone through a middle zone to a lower zone where the zones areconnected by valveless conduits. The lower zone may have a higherpressure than the upper zone. A body within the lower zone is inparticle communication a valveless conduit. The transfer of particlesfrom the upper zone to the lower zone is controlled by varying thepressure of the middle zone and the flow rates of gas passing upwardsthrough the valveless conduits. The body obstructs the particle flowwithin the lower zone.

In a broad embodiment, the invention is a method for transferringparticles from an upper zone, through a middle zone, to a lower zonecomprising: introducing a first gas stream into the lower zone;transferring particles downward from the upper zone to the middle zonethrough an upper valveless conduit, and transferring gas from the lowerzone upward through a lower valveless conduit into the middle zone;increasing the middle zone pressure; transferring particles downwardfrom the middle zone to the lower zone through the lower valvelessconduit, obstructing a particle flow in the lower zone with a particleimpervious body comprising a planar surface, and transferring gas fromthe middle zone upward through the upper valveless conduit into theupper zone; and decreasing the middle zone pressure.

In another broad embodiment, the invention is an apparatus fortransferring particles comprising: an upper zone; a middle zone; a lowerzone; a body located within the lower zone, the body being impervious tothe particles and comprising a planar surface; an upper valvelessconduit extending from the upper zone to the middle zone; a lowervalveless conduit extending from the middle zone to the lower zone, thelower valveless conduit comprising an outlet, the outlet being locatedabove and vertically aligned with the planar surface of the body; a gasinlet conduit providing fluid communication to the lower zone; and afirst gas conduit in fluid communication with the middle zone.

In another broad embodiment, the invention is a moving bed hydrocarbonconversion process comprising: contacting a catalyst moving downwardthrough a reaction zone with a hydrocarbon feed; withdrawing thecatalyst from the reaction zone; conveying the catalyst to aregeneration zone wherein the catalyst moves downward through theregeneration zone; withdrawing the catalyst from the regeneration zoneand passing the catalyst downward to an upper zone of a particletransfer apparatus; introducing a first gas stream into a lower zone ofthe particle transfer apparatus; transferring the catalyst downward fromthe upper zone to a middle zone of the particle transfer apparatusthrough an upper valveless conduit, and transferring gas from the lowerzone upward through a lower valveless conduit into the middle zone;increasing the middle zone pressure; transferring the catalyst downwardfrom the middle zone to the lower zone through the lower valvelessconduit, obstructing a catalyst flow in the lower zone with a particleimpervious body comprising an upper planar surface, and transferring gasfrom the middle zone upward through the upper valveless conduit into theupper zone; decreasing the middle zone pressure; and conveying thecatalyst from the lower zone to the reaction zone; wherein a pressure ofthe lower zone is greater than a pressure of the upper zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative view depicting the zones of the apparatus indifferent vessels and an embodiment of the body in the lower zone.

FIG. 2 is a representative view depicting another embodiment of the bodyin the lower zone and an arrangement of gas conduits used in anembodiment of the invention.

FIG. 3 illustrates other embodiments of the body, the gas conduits, andvalveless conduits encompassed by the invention and shows the zones ofthe apparatus may be within a single vessel.

FIGS. 4A-4C illustrate projections of the lower valveless conduit outletonto the planar surface of the body corresponding to FIGS. 1-3,respectively.

FIGS. 5A-5D illustrate additional configurations of the body within thelower zone and the lower valveless conduit that are encompassed by theinvention.

The Figures are intended to be illustrative of the invention and are notintended to limit the scope of the invention as set forth in the claims.The drawings are simplified diagrams showing exemplary embodimentshelpful for an understanding of the invention. Details well known in theart, such as cone deflectors, control valves, instrumentation, andsimilar hardware which are non-essential to an understanding of theinvention may not be shown.

DETAILED DESCRIPTION OF THE INVENTION

The invention may be used to transfer solid particulate matter from anupper zone, through a middle zone, to a lower zone where the lower zonepressure is greater than the upper zone pressure. The inventiontransfers particles without using moving equipment such as valves toblock the particle flow path. Generally, particles received in an upperzone are transferred through an upper valveless standpipe or transferconduit to a middle zone. A lower valveless standpipe or transferconduit is used to transfer the particles from the middle zone towardsan obstruction or body located within a lower zone. Thus the zones,valveless conduits, and obstruction or body may be in particlecommunication and the valveless conduits may provide particlecommunication.

The invention can be used within and/or between a variety of processunits to transfer particles, such as catalyst and adsorbents. The upperzone of the invention may receive particles from a separate process zoneand the lower zone may deliver the particles to another separate processzone. For example, an associated process unit may include a separatevessel that operates as a reaction zone which provides catalystparticles to the upper zone, and the lower zone may deliver catalyst toa separate process vessel such as a feed hopper of a pneumatic conveyingapparatus which in turn delivers the catalyst to the top of anotherreactor. In another embodiment, the invention may be arranged so thatthe upper zone and/or the lower zone are integrated with a process unitsuch that one or more process steps, or portions thereof, occurs withinthe upper and/or lower zones or the vessel(s) which contain the upperand/or lower zones. For example, the upper zone may be the lower portionof a reduction zone vessel or the entire reduction zone vessel of aprocess unit and/or the lower zone may be the upper portion of a surgevessel or the entire surge vessel of a process unit. The surge vessel inturn may introduce the particles into other zones of the same or adifferent process unit.

The invention may communicate with or the invention may comprise aportion of a process unit which provides for changing the fluid thatcontacts the particles. For example, the process unit may involvecontacting catalyst with a gas containing hydrocarbons and/or hydrogenin a reaction zone and removing carbon deposits from the catalyst usinga gas containing oxygen in a regeneration zone. As the catalyst istransferred between the reaction and regeneration zones, care must betaken to prevent mixing of the hydrocarbon/hydrogen atmosphere and theoxygen atmosphere. Examples of hydrocarbon conversion processes that mayemploy the invention include: alkylation, hydrorefining, hydrocracking,dehydrogenation, hydrogenation, hydrotreating, isomerization,dehydroisomerization, dehydrocyclization, and steam reforming. Onewidely practiced hydrocarbon conversion process that may employ theinvention is catalytic reforming using particles of catalyst. Exemplaryreaction and regeneration zones are disclosed in, e.g., U.S. Pat. No.5,858,210.

The upper, middle, and lower zones of the invention may be separatevessels or portions of separate vessels that are connected by valvelesstransfer conduits. In other embodiments, two or more of the upper,middle, and lower zones may be contained within a single vessel andseparated by dividers within the vessel. The upper, middle, and lowerzones of the invention may also provide one or more functions or processsteps of an associated process unit. In an embodiment, the upper,middle, and lower zones may be aligned sufficiently vertically to allowcatalyst to flow, at least in part, by gravity from at least one vesselat a higher elevation to at least one vessel at a lower elevation.

Flow of the particles into and out of the middle zone may be controlledby regulating the pressure of the middle zone, the flow rate of gasthrough each valveless particle transfer conduit, and the gas flow path.The same basic method steps may be accomplished by variousconfigurations of gas and particle conduits to introduce, vent, andchange the flow path of the gas used to control particle transfers. U.S.Pat. No. 4,576,712 and U.S. Pat. No. 4,872,969 disclose differentmethods and apparatus to control particle transfer and are herebyincorporated by reference in their entirety. The invention may use thesame basic method steps and is not limited to any particularconfiguration of the gas flow path and conduits. Existing configurationsand control schemes can be readily adapted to employ the invention.

The method of transferring particles from upper zone 10 to lower zone 30may be accomplished without blocking the particle transfer path withmoving equipment such as valves by repeating the following four stepcycle: 1) a fill or load step wherein particles are transferred from theupper zone to the middle zone; 2) a pressurization step wherein themiddle zone pressure is increased; 3) an empty step wherein particlesare transferred from the middle zone towards the obstruction or bodywithin the lower zone; and 4) a depressurization step wherein the middlezone pressure is decreased. The steps may overlap. For example, transferof particles may begin while the middle zone pressure continues toincrease or decrease and the middle zone pressure may begin to increaseor decrease while particles continue to transfer.

A single cycle results in the transfer of one batch of particles fromthe upper zone to the lower zone. The time required to complete onecycle, i.e. the cycle time, will depend on a variety of factorsincluding: the properties of the particles; the batch size, or amount ofparticles transferred per cycle; and the times needed to change thepressure of the middle zone. The invention is not limited by the cycletime. In an embodiment, the cycle time may be about 50 seconds. Inanother embodiment, the cycle time may be less than about 10 minutes,and the cycle time may be between about 2 minutes and about 4 minutes. Acontroller such as process control computers and programmablecontrollers may be used to regulate the cycle. The controller mayreceive various inputs, e.g. signals from particle level sensors,pressure gauges or indicators, differential pressure sensors, and timerssuch as for an individual step and/or the overall cycle. The controllermay also send signals for example to open, close, and adjust valves tocontrol the flow pattern and rate of various gas steams. Such acontroller and related signals are not shown in the figures as they arenot essential to the invention and are well known to the skilledartisan.

Broad embodiments of the invention will now be described with referenceto FIG. 1. In step 1 of the method, particles are transferred from upperzone 10 to middle zone 20 through upper valveless conduit 40. The upperand middle zones are at approximately the same pressure during step 1.Gas ascending through upper valveless conduit 40, if any, isinsufficient to retain the particles in conduit 40. During step 1, gasmay enter lower zone 30 through gas inlet conduit 11. Gas may also enterlower zone 30 from an associated process zone, not shown. Valve 12 mayregulate the quantity of gas flowing into lower zone 30; this flow ratemay be varied independently of the invention by means, not shown, forcontrolling the pressure of lower zone 30. The gas is selected to becompatible with the particles being transferred and may be the same gasas used in the associated process unit. Nitrogen, hydrogen, and air arenon-limiting examples of gas that may be used.

During step 1, gas flows upward from lower zone 30 through lowervalveless conduit 50 at a sufficient rate to retain the particles inconduit 50 thus causing middle zone 20 to fill with particles. Variousconfigurations of the gas flow path may be used. For example, a portionof the gas entering middle zone 20 from lower valveless conduit 50 mayflow through gas conduit 15 to upper zone 10 as shown in FIG. 2. Inother embodiments not illustrated, a portion of the gas may flow throughgas conduit 15 to another destination or simply be vented. In theembodiment illustrated in FIG. 3, which depicts the three zones of theapparatus in one vessel, upper valveless conduit 40 has a largerdiameter than lower valveless conduit 50 so that all gas entering middlezone 20 may flow through upper valveless conduit 40 at a flux which isinsufficient to retain the catalyst therein.

Upper 40 and/or lower 50 valveless particle transfer conduits may have arestriction, that is, a smaller cross-sectional area for particle flowthan the balance of the respective conduit. The cross-sectional areas ofthe restrictions if present and the balance of the conduit may be anyregular or irregular shape including a circle, oval, square, rectangle,and triangle. The cross-sectional area shape of a conduit may be thesame or it may differ over its length and may be the same or differentin the upper 40 and lower 50 valveless conduits. The cross-sectionalarea of a restriction and the balance of the conduit may have differentshapes or the same shape. The restriction may be located in a lowerportion of the conduit, that is, in the lower ⅓ of the respectiveconduit's height. The restrictions may be created in a wide variety ofways including crimping the conduit, using an insert, and forming theconduit with the restriction. Restrictions may be located proximate anoutlet in the lowermost end of the conduit. In an embodiment, theconduit, or a portion thereof is tapered toward the outlet to form therestriction at the outlet. The type, cross-sectional area shape, and/orlocation of restrictions in upper 40 and lower 50 valveless conduits maybe the same, or they may differ.

Step 1 ends when middle zone 20 is filled to its operating capacity withparticles. As shown in FIG. 1, upper valveless conduit 40 may extendinto middle zone 20 to define its operating capacity. That is, particlesstop flowing into the middle zone when particles in the middle zoneaccumulate to reach upper valveless conduit outlet 45. Thus, there maybe a continuous mass of particles from a lower portion of upper zone 10through upper valveless conduit 40, middle zone 20, and lower valvelessconduit 50. In another embodiment, the operating capacity of middle zone20 is predetermined and an optional upper level sensor, not shown, isused to detect when particles rise to this preset level. In such anembodiment, particles need not reach upper valveless conduit outlet 45and upper valveless conduit 40 need not extend past the shell of middlezone 20. In other embodiments, the operating capacity of middle zone 20may be determined by a preset time interval. Use of an adjustable timinginterval or high level set point enables the size of each particle batchto be varied from cycle to cycle. The particle levels and/or timeincrements may be measured and a signal sent to a controller to initiatestep 2 when the middle zone has been filled. Thus, particles maycontinue to flow into middle zone 20 for a time after step 2 begins ifthe particles are below upper valveless conduit outlet 45 at the end ofstep 1. In other embodiments, the particle flow may be stopped at thispoint in the cycle and the apparatus may be held with middle zone 20filled to its operating capacity until it is desired to continue theparticle transfer cycle. This portion of the cycle may also be known asa separate hold or ready step. For example, in the embodiment of FIG. 2,valve 16 is closed to force all the gas upwards through both valvelessconduits thereby stopping particles from flowing out of both the upperand middle zones. Similarly, in the embodiment of FIG. 3, valve 14 canbe opened in addition to valve 12 to accomplish the same effect.

In step 2 of the cycle, the pressure within middle zone 20 is increased.The middle zone pressure may be increased to stop the transfer ofparticles from the upper zone. In an embodiment, the middle zonepressure is increased to equilibrate with the higher pressure in lowerzone 30. This may be accomplished by introducing gas into middle zone 20through gas conduit 13. Gas to gas conduit 13 may be supplied from avariety of sources including, but not limited to: gas inlet conduit 11,lower zone 30, and separate supply sources such as facility headers andother zones in the associated or other process units. In the embodimentillustrated in FIG. 2, valve 14 is opened and valve 16 is closed topressurize middle zone 20. In the embodiment shown in FIG. 3, middlezone 20 is pressurized by opening valve 14 and closing valve 12. Thereis no need to change the gas flow path as the cycle moves from step 2 tostep 3. However, as explained above there are numerous ways of routingthe gas flow path to control the desired particle movement. Thus, theinvention encompasses changing the gas flow path between and/or withinsteps 2 and 3 to equilibrate the middle and lower zone pressures andretain particles within upper valveless conduit 40.

Step 3 may be referred to as the empty step of the cycle. As thepressures in the middle and lower zones equalize, particles begin toflow from middle zone 20 through lower valveless conduit 50 towardsobstruction or body 60 which is located within lower zone 30. That is,body 60 obstructs the particle flow within lower zone 30. During step 3,gas flows upward through upper valveless conduit 40 at a sufficient rateto prevent the transfer of particles from upper zone 10 into middle zone20. The level of particles in middle zone 20 falls as particles flow outof lower valveless conduit 50. A minimum particle level in middle zone20 may be used to decrease the length requirement of lower valvelessconduit 50. This may be accomplished in various ways such as using apreset time interval for the transfer, measuring the amount of particlesthat have entered lower zone 30, and measuring the level of particlesremaining in middle zone 20. For example, low level sensor 25 may detectthe absence of particles at the low level set point and send a signal toa controller to begin depressurizing or venting the middle zone, step 4.Multiple inputs may be used to manage the particle transfer cycle steps.In an embodiment, the length of step 3 may be controlled by a timer withlow level sensor 25 being used initiate step 4 early if the particlesfall below the minimum level set point.

In step 4, the depressurization step, the pressure in middle zone 20 maybe decreased to equilibrate the middle and upper zone pressures. Inanother embodiment, the middle zone pressure may be decreased to stopthe transfer of particles from the middle zone. This may be accomplishedfor example by re-establishing the gas flows that were used in step 1.Thus, in the embodiment of FIG. 2 valve 14 may be closed and valve 16opened so that the gas flux upward in lower valveless conduit 50 issufficient to retain particles therein while sufficient gas flowsthrough gas conduit 15 to equalize the pressure between the upper andmiddle zones. In other embodiments not illustrated, a portion of the gasmay flow through gas conduit 15 to another destination or simply bevented. In the embodiment illustrated in FIG. 3, valve 14 is closed andvalve 12 is opened to re-establish the gas flow path of step 1 of thatembodiment.

When the pressure of middle zone 20 is decreased in step 4 toequilibrate with upper zone 10 and increased in step 2 to equilibratewith lower zone 30 it is understood that the pressures in the two zones,superior and inferior, being equilibrated may or may not be the same.For example, pressure differences may exist, if there is some gas flowbetween the two equilibrated zones, or if they are being controlledindependently. Also, there is no requirement that the inferior zone beat the same or lower pressure than the superior zone of the two zonesbeing equilibrated. That is, particles may transfer from either superiorzone to the respective inferior zone even though the pressure of theinferior zone is higher than the pressure of the superior zone. The gasflow paths described for the embodiments of FIGS. 2 and 3 show that theinvention may provide for the continuous flow of gas to each of theupper, middle, and lower zones throughout a cycle. Further, theembodiment of FIG. 2 provides an uninterrupted flow of gas from thelower zone through the middle zone and into the upper zone throughoutthe cycle. In other embodiments not illustrated, various gas conduitsmay be used to control the middle zone pressure and the gas flow ratesthrough the upper and lower valveless particle transfer conduits toregulate the particle movement as herein described.

It is understood that the step numbers used herein are arbitrary and atransfer cycle may be considered to begin with any step and each step isemployed at least once during a cycle. The invention encompasses variousorders of the steps and some steps may be repeated in the course oftransferring a single batch of particles from the upper zone to thelower zone. For example, the transfer of particles in steps 1 and/or 3may be interrupted by employing steps 2 and 4 multiple times during atransfer cycle. Thus, in an embodiment, the order of steps may be1—transfer particles from the upper zone to the middle zone; 2—increasethe middle zone pressure to stop the transfer of particles; 4—decreasethe middle zone pressure to equilibrate the middle and upper zonepressures; 1—transfer particles from the upper zone to the middle zone;2—increase the middle zone pressure to equilibrate the middle and lowerzone pressures; 3—transfer particles from the middle zone towards thebody within the lower zone; and 4—decrease the middle zone pressure toequilibrate the middle and upper zone pressures. In another embodimentthe order of steps may be 1, 2, 4, 1, 2, 3, 4, 2, 3, and 4. Other stepssuch as purging the middle zone may be included in a transfer cycle.

Returning to the discussion of step 3, obstruction or body 60 is locatedwithin lower zone 30 to obstruct the particle flow within lower zone 30.Outlet 55 of lower valveless conduit 50 is located above and verticallyaligned with planar surface 62 of the body. That is, outlet 55 islocated vertically above and horizontally within the planar surface.Body 60 may be spaced apart from the inside surface of the lower zoneand secured via one or more support elements 67 as in FIG. 1. Forexample, the body 60 may be suspended such as by wires or rods 67′ inFIG. 2; fastened to or supported by relatively horizontal rails or beams67″ in FIG. 3; or located on a stand secured to a lower portion of thezone. Such supports which are known in the art may be used in anycombination to locate the body 60 relative to the lower valvelessconduit 50 as described herein. These support elements may in turn besecured to any inside surface of the lower zone or any other internalstructures within the lower zone including lower valveless conduit 50.The body and support elements may be of the same or different materialof construction suitable for the process conditions. In an embodiment,the support is of the same material of construction as that of the lowerzone inside surface.

In the embodiment of FIG. 1, outlet 55 of lower valveless conduit 50 islocated vertically above planar surface 62 of body 60. Outlet 55 may bevertically spaced apart from planar surface 62. Body 60 may be a solidimperforate object or it may comprise one or more perforations thatpermit gas to flow through the body. As used herein, “perforations”includes holes, gaps, slots, other openings, and combinations thereofwhich are sufficiently small to prevent the particles from passingthrough the body. The body may be impervious to the particles beingtransferred, that is, a particle impervious body. Outlet 55, as depictedin FIG. 1, may be a uniform distance, D, above planar surface 62, whichmay be an upper planar surface. Body 60 obstructs the particle flow asparticles emerge or are discharged from outlet 55 of lower valvelessconduit 50 towards planar surface 62 which may be horizontal. Particlesmay bounce, roll, or otherwise be diverted off the planar surface andpass to the portion of lower zone 30 below the planar surface. Particlesdischarged from outlet 55 may strike other particles which haveaccumulated on the planar surface and be deflected or diverted aroundbody 60 5 without actually making contact with the body itself. Theparticle flow within the lower zone is obstructed by a particleimpervious body in this embodiment.

Lower valveless conduit 50 preferably extends into lower zone 30 asshown in FIG. 1, though this extension into lower zone 30 is notrequired. Outlet 55 of lower valveless conduit 50 is also locatedhorizontally within planar surface 62. That is, a projection of outlet55 10 downward onto planar surface 62 in the lower zone may be depictedas illustrated in FIG. 4A.

The inner surface of lower valveless conduit 50 at the outlet 55 definesthe outlet perimeter 58 which is horizontally within the perimeter 68 ofplanar surface 62 as shown by the projection of outlet perimeter 58 onplanar surface 62. In the embodiment illustrated in FIG. 4A, outletperimeter 58 and planar surface perimeter 68 are concentric circles andthus are spaced apart by 1 5 a constant horizontal distance, R. FIG. 4Aalso shows horizontal separation between the planar surface perimeter 68and the inner surface 31 of the lower zone.

Body 60 may be fabricated in any shape sufficient to obstruct particlesdischarged by lower valveless conduit 50 during step 3. Particles mayaccumulate or mound on the body planar surface during step 3 and mayreach a level to contact the lower valveless transfer conduit 20 outlet55. That is, body 60 and lower valveless conduit 50 are configured tofacilitate forming a continuous mass of particles between middle zone 20and body 60 through lower valveless conduit 50 during a portion of theparticle transfer cycle. The continuous mass of particles comprisesparticles contacting the body, particles within the lower valvelessconduit, and particles within the middle zone. Though it is preferred toform this continuous mass of particles 25 during each particle transfercycle, this is not required. The invention will continue to transferparticles from the upper zone to the lower zone as described even ifthis continuous mass of particles in not formed. The nature of theparticles is one variable or factor which affects the formation of theparticle mound or pile. It is well known to those skilled in the art ofdesigning solids flow systems to conduct experiments to determine flowcharacteristics of the particular 30 solid involved. The angle of reposeof the particles is a well known property of particles that isdetermined by depositing the particles on a horizontal surface withnegligible velocity to form a pile. The angle formed between the slopeof the pile and the horizontal surface is the angle of repose. SeeAndrew W. Jenike, Storage and Flow of Solids, Bulletin No. 123 of theUtah Engineering Experiment Station Sixth Printing (revised), March,1970, University of Utah.

Under the test conditions for determining the angle of repose, theheight of the mound formed equals the horizontal distance between thedischarge point and the perimeter of the mound's base multiplied by thetangent of θ where θ is the angle of repose in degrees. However,conditions during particle transfer with the invention may varysubstantially from the conditions used to determine the angle of reposeand the height of the particle mound in the invention may be greater orless than that obtained when determining the angle of repose. Manyvariables may affect the formation and slope of the particle mound onthe planar surface and whether the particles will reach a heightsufficient to contact the lower valveless transfer conduit outlet 55.Non-limiting examples of such variables may include: the particlevelocity towards the planar surface, the gas flow paths and velocities,the difference in pressure between the middle and lower zones, theparticle transfer rate, the particle height in the middle zone, andparticle variables such as the coefficients of friction between theparticles and between the particles and the planar surface, the particlesize, shape, and variations in the size and shape.

The continuous mass of particles may be formed during step 3. Particlesmay transfer from conduit 50 towards the body planar surface 62 at agreater rate than the particle transfer rate from the planar surface asthe particles pass off the planar surface perimeter to the volume of thelower zone below the planar surface. Particles may continue to transferfrom the middle zone into the lower zone towards body planar surface 62moving as a continuous mass. The height of particles on the planarsurface may fall below conduit outlet 55 as the particle transfer ratefrom conduit 50 decreases. Similar to the transition to step 2,pressurization, particle transfer towards the body planar surface 62 maycontinue during a portion of step 4, depressurization. Also, particletransfer from the planar surface 62 to the volume of the lower zonebelow the planar surface may continue during at least a portion of step4. The size of the planar surface is at least sufficient to encompassthe projection of outlet 55 and provide an area for particles to moundtowards the outlet. The planar surface size is constrained by the designof the lower zone. There must be a sufficient space between the planarsurface and the inner surface of the lower zone to accommodate theparticle transfer rate.

The vertical distance, D, between outlet 55 and planar surface 62 may belimited to a maximum value. In an embodiment, the vertical distance, D,separating the planar surface 62 and lower valveless conduit outlet 55is no more than about 1.25*R*tan θ, where R is the horizontal distanceseparating the outlet perimeter 58 and the planar surface perimeter 68and θ is the angle of repose of the particles in degrees. In anotherembodiment, D is no more than about 1.15*R*tan θ; and D may be no morethan about 1*R*tan θ. Likewise, the vertical distance, D, separatingoutlet 55 and planar surface 62 must be sufficient to discharge theparticles being transferred and D may be limited to a minimum value. Inan embodiment, the vertical distance, D, is at least about five timesthe average particle diameter. In another embodiment, D is at leastabout 0.35*R*tan θ; and D may be at least about 0.75*R*tan θ. In anembodiment, the vertical distance, D, may be limited to a range betweena minimum value and a maximum value. For example, D may range from leastabout 0.35*R*tan θ to about 1.25*R*tan θ, and in another embodiment Dmay range from least about 0.75*R*tan θ to about 1.25*R*tan θ. The abovelimitations may apply and are easy to assess in some embodiments whenoutlet 55 and outlet perimeter 58 are a uniform vertical distance aboveplanar surface 62 and the horizontal distance, R, separating outletperimeter 58 and planar surface perimeter 68 is uniform. However, theinvention encompasses many different configurations of the lowervalveless conduit, diverse particles, and operating conditions each ofwhich may impact the relationship between vertical distance D andhorizontal distance R.

In the embodiment of FIG. 2, body 60 comprises floor 61, side walls 63and retained particles that define the planar surface 62 of the body.Thus, the body may be unitary or it may comprise various similar ordissimilar elements to obstruct the particle flow and define the planarsurface. As shown, some particles may be retained by the body. Althoughthe particles cannot pass through the particle impervious body, theretained particles may be moved or displaced from the body such as bythe impact of other particles. In another embodiment, the retainedparticles may be fixed in place by any conventional technique such aswelding, gluing, and covering with a screen or grate. When the particlesbeing transferred also define a portion of the planar surface, they maybe added to the body during operation in the first or subsequentparticle transfer cycles. As illustrated in FIG. 2, side walls 63 may bevertical and define the perimeter 68 of planar surface 62. In otherembodiments not illustrated, the side walls may be angled to create aplanar surface which is larger or smaller than the surface area of thebase. The use of particles, affixed or not, to define at least part ofthe planar surface exemplifies that the planar surface or a portionthereof may be irregular, rough, and uneven. Particles that define, atleast in part, the planar surface may be different than the particlesbeing transferred. In such an embodiment it is preferred that thesurface particles be affixed to the body if displacement into the restof the apparatus or process would be detrimental.

This embodiment illustrates that the location of the planar surface maybe defined by where the base of the particle mound forms. For example,additional particles deposited on the mound may slide, roll, orotherwise travel down the slope of the mound and off the mound along theplane of the mound's base. Also, the perimeter of the planar surface andthe perimeter of the particle mound, or portions thereof, may coincidesuch that the particles fall from the coincident perimeters to a lowerelevation without creating another larger mound having a base in a lowerplane. Thus, as illustrated in FIG. 2, the upper surface of body floor61 is not the planar surface. Particles traveling down the slope of theformed mound do not travel along or fall from the upper surface of bodyfloor 61. Rather, the planar surface 62, illustrated by the dashed line,is the imaginary, two-dimensional plane that is defined by the uppersurfaces of the side walls as the base of the particle mound will format this elevation. Similarly, an imaginary plane may be used to definethe planar surface when the surface is rough or includes smallirregularities.

FIG. 4B illustrates the downward projection view of the embodiment ofthe lower zone of FIG. 2 showing outlet perimeter 58 may be a squarewithin a rectangular planar surface perimeter 68. Again, the planarsurface 62 is spaced apart from the inner surface 31 of the lower zoneto allow particles to pass to the lower portion of the zone 30 below theplanar surface. As shown, there is no requirement for the crosssectional areas or perimeters of the outlet 55 and planar surface 62 tobe of any particular shape or have the same shape or be equidistantlyspaced apart. As also shown, there is no requirement that the outlet 55or planar surface be centered in the lower zone. Outlet 55 of lowertransfer conduit 50 and body 60 are configured with the outlet beinglocated vertically above and horizontally within the planar surface.That is, outlet 55 is above and vertically aligned with planar surface62 and the body obstructs the particle flow within the lower zone.

When the vertical distance, D, between outlet 55 and planar surface 62is uniform and the horizontal distance, R, between the perimeters of theoutlet and the planar surface varies as in this embodiment,relationships specified between D and R, if any, may be more specific.For example, if the particle mound reaches the outlet perimeter where Ris at its minimum value as illustrated, then the particle mound willreach the entire perimeter of the outlet barring any unusual conditionssuch as localized gas flows. Thus, a maximum vertical distance may bedefined as D being no more than about 1.25*R*tan θ where R is theminimum value of R. In another embodiment, the particles do not reachthe outlet where R is at the minimum value, but at another locationalong the perimeter of the outlet. Thus, the continuous mass ofparticles may be formed even though the mound does not reach allportions of the outlet. That is, the relationship between D and R mayneed to be evaluated such that D is determined at each point along theoutlet perimeter and the corresponding value of R is the minimumhorizontal distance from that point to the perimeter of the planarsurface. If a minimum vertical distance is defined such that D is atleast about 0.35*R*tan θ, it may be sufficient for this to be satisfiedat the portion of the outlet perimeter where R is at its minimum value.It is not necessary that each portion of the outlet perimeter satisfy aminimum vertical distance requirement. As long as the particle mounddoes not prevent the flow of particles, the invention will operate. Forexample, particles may be able to travel down the mound, such as, movingin a continuous mass downward with the mound and/or traveling down theslope of the mound, and pass off the planar surface to the lower portionof lower zone 30 at a portion of the perimeter sufficient for theparticle transfer rate. The transfer rate of particles from outlet 55may vary even within step 3 and the particles may stop flowing for briefperiods of time.

As illustrated in FIG. 3 and corresponding FIG. 4C, the outlet 55 oflower valveless conduit 50 may be configured to have a circularperimeter, but with half of the outlet perimeter being spaced apart fromthe planar surface 62 by a distance, D₁, while the other half of theoutlet perimeter is spaced apart from the planar surface 62 by adistance, D₂. FIG. 4C illustrates as discussed above that therelationship specified between D and R, if any, may be determined foreach D_(N) and corresponding R_(N). In an embodiment, the continuousmass of particles between the body and the middle zone may be formedwhen the mound of particles on the planar surface reaches one or morepoints along the perimeter of outlet 55. In another embodiment, aportion of the outlet perimeter may be sufficiently spaced above theplanar surface to enable the transfer of particles while another portionof the outlet perimeter is spaced closer to or even contacts the planarsurface. It is not necessary for particles to transfer at every pointalong the outlet's perimeter. For example, it may be sufficient that atleast about 25% of the outlet perimeter be spaced vertically above theplanar surface by a distance of at least about five times the averageparticle diameter. In another embodiment, at least about 10% of theoutlet perimeter is spaced vertically above the planar surface by adistance, D where D is at least about 0.35*R*tan θ. The portion of theoutlet perimeter meeting such embodiments need not be at the samevertical height above the planar surface and need not be a continuousportion of the outlet perimeter.

FIGS. 5A-5D illustrate a few non-limiting configurations of the lowervalveless transfer conduit 50 and the obstruction or body 60 which areencompassed by the invention. Although the configurations differ, thesame reference numerals are used to identify the corresponding elementsin each Figure. As in FIGS. 4A-4C, the support element(s) are notillustrated in these views as they are not necessary for anunderstanding of the configurations. It is readily apparent that myriadother configurations are encompassed by the invention.

FIG. 5A shows planar surface 62 of body 60 may be offset from thehorizontal by an angle β. Generally, as this angle, β, between planarsurface 62 and the imaginary horizontal plane increases, the verticaldistance D between the planar surface 62 and outlet 55 should bedecreased to facilitate formation of the particle mound. It is preferredthat angle β be no more than angle θ, the angle of repose of theparticles being transferred. That is, the planar surface may be within θdegrees of horizontal. In an embodiment, the planar surface may bewithin 0.5*θ degrees of horizontal, and in another embodiment, theplanar surface may be within 0.25*0 degrees of horizontal. A slopedplanar surface may be configured with a vertically non-uniform outlet 55as show or with a vertically uniform outlet. As before, D may bedetermined at each point along the perimeter 58 of outlet 55 asillustrated by D₁ and D₂.

As shown in FIG. 5B, lower valveless conduit 50 need not extend intolower zone 30 and more than one such conduit may be used. Both outlets55 are located vertically above and horizontally within planar surface62. Although body 60 may comprise multiple planar surfaces, the planarsurface of the invention may be defined as the planar surface that wouldsupport or define the base of the particle mound. Thus, where the slopeof the sides of the body are vertical as in other embodiments or notvertical but too steep as in this embodiment to support a particlemound, the planar surface 62 and its perimeter 68 are defined by theupper surface which may support a particle mound. There is norequirement that the sides of the body are sloped uniformly and one sidemay be sloped or comprise other planar surfaces to support a particlemound and thus be part of the planar surface defining a lower perimeterwhile another side is not part of the planar surface. Thus, the planarsurface need not be located in a single horizontal plane. As illustratedby a number of the embodiments herein, planar surface 62 may be an upperplanar surface or the uppermost planar surface of body 60, but this isnot required. Body 60 may comprise any number of protrusions orextensions that form planar surfaces which may or may not be covered byparticles but which do not define the planar surface of the inventionbecause the elevated planar surface does not define the base of theparticle mound.

FIG. 5C illustrates that a portion of planar surface 62 may abut or beattached to the inner surface of the lower zone and another portion ofthe planar surface may be spaced apart from the inner surface of thelower zone. Such a configuration may impact the formation of a particlemound. For example, the inner surface of the zone may act as a side walland particles unable to pass off the planar surface at that location mayraise the planar surface closer to outlet 55 as discussed in FIG. 2.This embodiment also highlights that the relationship between D and R todefine a minimum D (or equally a maximum R), if any, considers R wherethe particles may pass freely from the perimeter of the planar surfaceand the particles are not blocked such as by the inner surface of thelower zone. This embodiment also shows that the lower valveless conduit50 need not be strictly vertical, but may be angled relative to truevertical. Also, a conduit may be tapered along its entire length or aportion thereof towards outlet 55. In other embodiments, not shown,tapering of a valveless conduit towards the outlet does not require anextensive distance along the conduit. These non-vertical and taperingembodiments may also be used in upper conduit 40. These conduitconfigurations may be used independently.

FIG. 5D illustrates another embodiment of the invention wherein outlet55 is located vertically above and horizontally within planar surface 62of body 60. Although body 60 may retain particles on planar surface 62,body 60 does not have an internal particle retention volume. Body 60 maycomprise at least one passageway 65 which provides particlecommunication from the planar surface through the body to the volume ofthe lower zone below the body. The use of one or more such passagewaysprovides another path for the particles to pass through the lower zone.The configuration of passageway 65, such as the size, number, locationthrough the body, geometry, and other parameters may be varied to obtainthe desired particle flow. All of the particles may flow through thepassageway or passageways. In another embodiment a portion of theparticles may pass through the passageway(s) and another portion of theparticles may pass over or around the perimeter of the planar surface ofthe body. Similar to the use of a sloped planar surface, a passagewaythrough the body may help ensure that after a continuous mass ofparticles from the body through the lower valveless conduit to themiddle zone is formed, this mass does not prevent the continued transferof particles. As described above, the invention may include a transitorymass of particles comprising particles contacting the planar surface,particles within the lower valveless conduit, and particles within themiddle zone as the particle cycle progresses.

By regulating the particle transfer rate towards the planar surface ofthe body for a given configuration of the lower valveless conduit andthe body, the formation and continued existence of the continuous massof particles from the middle zone to the body may be controlled. In anembodiment, this continuous mass of particles may exist for a portion ofstep 3. In another embodiment, the continuous mass of particles mayexist for a portion of step 4; and the height of the particle mound onthe body planar surface 62 may fall below the level of conduit outlet 55before the beginning of step 1. Thus, particles may transfer from theplanar surface to the volume of lower zone 30 below the planar surfaceduring step 4. In yet another embodiment, planar surface 62 isconfigured to release essentially all of the particles that haveaccumulated on the planar surface before the subsequent step 3 such asby having a non-horizontal planar surface. This configuration alone orin combination with other parameters such as the smoothness of thesurface, the relationship between D and R, and the uniformity of thatrelationship may facilitate the particles sliding, rolling, or otherwisefalling off the planar surface. That is, at least some particlesdischarged from outlet 55 may contact the planar surface when step 3begins. Lower valveless conduit 50 provides particle communication tothe planar surface 62 of body 60, and lower valveless conduit 50 and thebody or planar surface may be in particle communication even if thelower valveless conduit and body or planar surface are not connected.

During the particle transfer cycle, the inventory in upper zone 10 maybe continuously and/or intermittently replenished with particles such asfrom an associated or integrated process zone and/or as added from afresh particle feed hopper. Likewise, particles delivered to lower zone30 may be withdrawn from or pass out of the lower zone continuouslyand/or intermittently. It is preferred that an inventory or surge volumeof particles be maintained in both the upper and lower zones throughoutthe particle transfer cycle. As previously described, upper zone 10 mayalso provide one or more functions of an associated or integratedprocess unit including regeneration zones. Non-limiting examplesinclude: a particle feed hopper, a reaction zone, an atmosphere purgezone, another catalyst transfer zone, a reduction zone, and anelutriation zone. The internal pressure of upper zone 10 may beindependently controlled by means well known in the art. For example,upper zone 10 may be in fluid communication with a process zone so thatthe upper zone pressure depends upon and varies with the pressure inthat process zone. The upper zone pressure is not critical and may beatmospheric, sub-atmospheric, or super atmospheric.

Lower zone 30 may be a holding vessel, or surge zone from which theparticles are transferred by other means such as pneumatic conveying. Inother embodiments, lower zone 30 may provide one or more functions of anassociated or integrated process unit including regeneration zones.Non-limiting examples include: a particle feed hopper, a reaction zone,an atmosphere purge zone, another catalyst transfer zone, a reductionzone, and an elutriation zone. The internal pressure of lower zone 30may be independently controlled by means well known in the art. Forexample, lower zone 30 may be in fluid communication with a process zoneso that the lower zone pressure depends upon and varies with thepressure in that process zone. In an embodiment, the upper zone pressuremay be higher than the lower zone pressure for a portion of the transfercycle. In another embodiment, lower zone 30 may be maintained at ahigher pressure than upper zone 10. For example, upper zone 10 may bemaintained at a nominal pressure of 34 kPa (g) and permitted to varywithin a range from about 14 to about 55 kPa (g) while the nominalpressure of lower zone 30 may be 241 kPa (g) within a range from about207 to about 276 kPa (g). In another embodiment, upper zone 10 may bemaintained at a nominal pressure of 241 kPa (g) and permitted to varywithin a range from about 172 to about 310 kPa (g) while the pressure oflower zone 30 may be within a range from about 345 to about 2068 kPa(g). Thus, the differential pressure between the lower zone 30 and upperzone 10 might range from about 35 to about 1896 kPa. However, thisinvention may be used when the pressure differential between zones is aslittle as about 0.7 kPa and in excess of 2000 kPa. Middle zone 20 servesas an intermediate zone, and its nominal pressure is adjusted toregulate the flow of the particles.

The apparatus of the invention may be used as a solids flow controldevice for an entire process, since the flow rate of particles from theupper zone to the lower zone can be varied, as discussed above. Theupper, middle, and lower zones may contain other non illustratedapparatus known in the art such as baffles, screens, and deflector coneswhich may be used to facilitate particle flow and/or direct theparticles or the gas through a zone in a desired manner. The componentsof the present invention may be fabricated from suitable materials ofconstruction, such as metals, plastics, polymers, and composites knownto the skilled artisan for compatibility with the particles, andoperating conditions, e.g. gas, temperature, and pressure. The size,shape, and density of the particles is only limited by the size of theequipment and the type and flow rates of the gas or gases used. In anembodiment, the particles are spheroidal and have a diameter from about0.7 mm to about 6.5 mm. In another embodiment, the particles have adiameter from about 1.5 mm to about 3 mm. The particles may be catalystsan example of which is disclosed in U.S. Pat. No. 6,034,018.

As previously noted, particle transfer apparatus of the prior art may beadapted to incorporate the invention. Likewise, standard engineeringprinciples especially those related to the flow of solids and gases andknown design methods may be used in this invention. In addition to theteachings herein, the design considerations and methodology described inU.S. Pat. No. 4,576,712 and U.S. Pat. No. 4,872,969 may be used topractice this invention. For example, the pressure in the upper andlower zones, the minimum and maximum gas flow rates upwards through thezones and the valveless conduits, and the required particle transferrate are design factors that are often fixed by the associated processunit. The length of the particle column inside the valveless conduit,the height of particles in the zone above the valveless conduit, and thediameter of the conduit may be balanced so that changing the pressuresand gas flow paths as described herein controls whether particles willflow down through or be retained within the conduit. The design methodincludes limiting the gas flow rates and pressure differentials to avoidfluidizing particles within the zones and to prevent particles frombeing suddenly forced up or down the valveless conduits.

Thus, it is known that the internal pressures of the upper and lowerzones, the minimum and maximum gas flow rates, the identities of the gasand the particles, and the required range of particle transfer rates,may be used to determine various parameters of the invention. Theseparameters include: the normal minimum and maximum volumes occupied bythe particles in the zones, the particle heights required in the zonesabove the transfer conduits, the diameter of the transfer conduits, andthe lengths of the transfer conduits. These and other parameters such asthe gas conduit size and arrangement may characterize a particularembodiment encompassed by the invention.

In an embodiment, a hydrocarbon feed is contacted with catalystparticles moving downward through a hydrocarbon conversion processreaction zone. The catalyst is withdrawn from the reactor and conveyedupwards to a top portion of a regeneration zone. The catalyst passesdownward through the regeneration zone undergoing one or more treatmentsteps. The catalyst is withdrawn from the regeneration zone and passeddownward to an upper zone of a particle transfer apparatus. The upperzone pressure may be less than the reaction zone pressure. The particletransfer apparatus transfers the catalyst from the upper zone to thelower zone wherein the catalyst flow is obstructed by a particleimpervious body as described above. The catalyst, now at a higherpressure, may be conveyed upwards to a top or upper portion of thereaction zone by a known pneumatic transport system such as described inU.S. Pat. No. 5,716,516 and U.S. Pat. No. 5,338,440.

Moving bed systems and processes which employ them are well known in theart. See for example U.S. Pat. No. 3,725,249 and U.S. Pat. No.3,692,496. The reaction zone is oriented substantially vertically (i.e.sufficiently vertical for catalyst to flow downward at least in part bygravity) and may be divided into multiple reactors or sub zones, forexample, to manage the heat of reaction. The reaction zone may consistof a single vertical stack of one or more sub zones, or the reactionzone may be split into two or more vertical stacks to manage structuralheight limitations. A stack may comprise more than one vessel. It isalso important to note that the reactants may be contacted with thecatalyst bed in either an upward, downward, or radial flow fashion withthe latter being preferred. In addition, the hydrocarbon feed may be inthe vapor phase when contacting with the catalyst bed. That is, thecatalyst moves gradually downward in the reaction and regeneration zonesas a non-fluidized, dense phase or compact bed that is withdrawn fromthe bottom or lower portion of the reaction and regeneration zones andis replenished by adding catalyst to the top portion of these zones. Thecatalyst withdrawn from the reaction zone is lifted to the top of theregeneration zone by equipment known in the art including mechanicaldevices such as screw or bucket conveyors or star valves. Preferably,the catalyst is lifted by a pneumatic transport system.

In the reaction zone, the catalyst may deactivate over time by one ormore mechanisms including deposition of carbonaceous material or cokeupon the catalyst, sintering or agglomeration of catalyst metals, lossof catalytic promoters such as halogens, and exposure to the reactionatmosphere at reaction temperatures up to 760° C. and pressures rangingfrom about 0 to about 6,900 kPa(g). As used herein, “reactiontemperature” means the weighted average inlet temperature (WAIT), whichis the average of the inlet temperature to the first bed of catalystcontacted with the feed and each subsequent bed of catalyst following aheating or cooling stage to manage the heat of reaction weighted by thequantity of catalyst in the corresponding reactor. Frequently, thereaction conditions include the presence of hydrogen that may beintroduced separately or combined with the hydrocarbon feed. Hydrocarbonproducts from the reactor are often cooled and separated into vapor andliquid streams such as in a flash drum or vapor/liquid separator. All ora portion of the vapor stream, containing hydrogen may be recycled tothe reaction zone while the liquid stream may be sent to storage,blended with other streams or processed further.

The regeneration zone is designed and operated to restore or rejuvenatethe catalyst performance and may include multiple zones and/or treatmentsteps. Non-limiting examples include a burn or combustion zone, ahalogenation zone, a drying zone, and a cooling zone. The regenerationzone may include other known zones such as an elutriation zone and adisengaging zone. The regeneration zone may comprise one or more vesselswhich are substantially vertically aligned in one or more stacks.Additional regeneration zone details are available in the art such asU.S. Pat. No. 6,034,018. The regeneration zone may operate at a pressureranging generally from about 0 to about 6900 kpa(g) and a temperaturefrom about 370° C. to about 538° C. Often, the regeneration zoneincludes an atmosphere containing oxygen in contrast to the reactionzone hydrocarbon/hydrogen atmosphere. Thus, separation of the reactorand regenerator atmospheres may be important to prevent undesirable sidereactions. Various known elements such as nitrogen seals or bubbles,isolation valves, and pressure differentials to maintain desired purgesand gas flows may be used to prevent the hydrogen and oxygen atmospheresfrom mixing.

The catalyst being withdrawn from the reaction zone may be purged withhydrogen to keep excess hydrocarbons in the reaction product stream. Inan embodiment, the reaction zone atmosphere such as hydrogen and/orremaining hydrocarbon gas surrounding the catalyst is purged withnitrogen before the catalyst enters the oxygen containing atmosphere.Oxygen may be introduced to the regenerator vessel, or oxygen may beadded upstream of the regenerator, for example, in a disengaging vesselor isolation valves of the regeneration zone. This change from thereaction zone atmosphere to an inert or nitrogen atmosphere may beconducted before or after the catalyst is lifted or conveyed from thebottom of the reaction zone to the top of the regeneration zone.Likewise, the change from the regeneration zone oxygen atmosphere may beaccomplished by a nitrogen purge followed by introduction of a reactionzone gas or reducing gas, such as hydrogen. This atmosphere change isusually completed below the regeneration zone before the catalyst entersthe upper zone of the particle transfer zone or apparatus. However, thisatmosphere change may be accomplished within the particle transferapparatus or after the catalyst exits the particle transfer apparatus,before or after the catalyst is lifted to the top of the reactor zone.Low pressure differentials ranging for example from about 2 to about 14kPa may be sufficient to maintain proper nitrogen purges or flows tokeep the regeneration and reaction zone atmospheres separated. Catalystmay be purged with nitrogen in a conduit or the catalyst may enter anitrogen containing vessel as it moves through the process.

The catalyst may also undergo a reduction step. If needed, the reductionstep is normally performed after the catalyst leaves the regeneratorvessel when the catalyst is under a reducing gas or reaction zone gasatmosphere. In an embodiment, the reduction step occurs in the upperzone of the particle transfer apparatus. In another embodiment, thereduction step occurs in a reduction zone located atop the reactor inthe reaction zone. Typical reduction conditions include an atmospherecomprising hydrogen, a temperature ranging from about 315° C. to about540° C., and a super atmospheric pressure.

In an embodiment, the hydrocarbon conversion process is a reformingprocess which is well known in the petroleum refining and petrochemicalindustries. In brief, the reforming feed comprises a petroleum fractionknown as naphtha which may have an initial boiling point from about 40°C. to about 120° C. and an end boiling point from about 145° C. to about218° C. In an embodiment, the naphtha has an initial boiling point fromabout 65° C. to about 104° C. and an end boiling point from about 150°C. to about 195° C. The naphtha feed may be a straight run petroleumfraction and/or obtained as a product from one or more petroleum andpetrochemical processes such as hydrocracking, hydrotreating, FCC,coking, stream cracking, and any other process which produces ahydrocarbon product in the naphtha boiling range. A number of 30different reactions may occur in a reforming process including thedehydrogenation of cyclohexanes and dehydroisomerization ofalkylcyclopentanes to yield aromatics, dehydrogenation of paraffins toyield olefins, dehydrocyclization of paraffins and olefins to yieldaromatics, isomerization of paraffins, isomerization ofalkylcycloparaffins to yield cyclohexanes, isomerization of substitutedaromatics, and hydrocracking of paraffins. As a result, reforming is anoverall endothermic process and it is common to use more than onereaction zone to allow reheating of the reactants in order to obtain thedesired performance.

Reforming conditions may include reaction temperatures from about 425°C. to about 580° C., preferably from about 450° C. to about 560° C.; apressure from about 240 kPa(g) to about 4830 kPa(g), preferably fromabout 310 kPa(g) to about 1380 kPa(g); and a liquid hourly spacevelocity (LHSV), defined as liquid volume of fresh feed per volume ofcatalyst per hour, from about 0.2 to about 10 hr⁻¹. The reformingreaction is carried out in the presence of sufficient hydrogen toprovide a hydrogen/hydrocarbon mole ratio from about 0.5:1 to about10:1. A reforming catalyst typically comprises one or more noble metals(e.g., platinum, iridium, rhodium, and palladium), a halogen component,and a porous carrier or support, such as an alumina. Exemplary catalystsare disclosed in U.S. Pat. No. 6,034,018. The regeneration zone pressuremay range from about 0 kPa(g) to about 345 kPa(g). In an embodiment, theregeneration zone pressure ranges from about 0 kpa(g) to about 103kPa(g), and in another embodiment from about from about 172 kpa(g) toabout 310 kPa(g).

The hydrocarbon conversion process may be a dehydrocyclodimerizationprocess wherein the feed comprises C₂ to C₆ aliphatic hydrocarbons whichare converted to aromatics. Preferred feed components include C₃ and C₄hydrocarbons such as isobutane, normal butane, isobutene, normal butene,propane and propylene. Diluents, e.g. nitrogen, helium, argon, and neonmay also be included in the feed stream. Dehydrocyclodimerizationoperating conditions may include a reaction temperature from about 350°C. to about 650° C.; a pressure from about 0 kPa(g) to about 2068kPa(g); and a liquid hourly space velocity from about 0.2 to about 5hr⁻¹. Preferred process conditions include a reaction temperature fromabout 400° C. to about 600° C.; a pressure from about 0 kPa(g) to about1034 kPa(g); and a liquid hourly space velocity of from 0.5 to 3.0 hr⁻¹.It is understood that, as the average carbon number of the feedincreases, a reaction temperature in the lower end of the reactiontemperature range is required for optimum performance and conversely, asthe average carbon number of the feed decreases, the higher the requiredreaction temperature. Details of the dehydrocyclodimerization processare found for example in U.S. Pat. No. 4,654,455 and U.S. Pat. No.4,746,763.

The dehydrocyclodimerization catalyst may be a dual functional catalystcontaining acidic and dehydrogenation components. The acidic function isusually provided by a zeolite which promotes the oligomerization andaromatization reactions, while a non-noble metal component promotes thedehydrogenation function. Exemplary zeolites include ZSM-5, ZSM-8,ZSM-11, ZSM-12, and ZSM-35. One specific example of a catalyst disclosedin U.S. Pat. No. 4,746,763 consists of a ZSM-5 type zeolite, gallium anda phosphorus containing alumina as a binder. Multiple reactors orreaction zones may be used to manage the heat of reaction as describedabove for the reforming process. The dehydrocyclodimerization processregeneration zone pressure may range from about 0 kpa(g) to about 103kPa(g). In a particular embodiment, the regeneration conditions mayinclude a step comprising exposing the catalyst to liquid water or watervapor as detailed in U.S. Pat. No. 6,657,096.

In an embodiment, the hydrocarbon conversion process is adehydrogenation process for the production of olefins from a feedcomprising a paraffin. The feed may comprise C₂ to C₃₀ paraffinichydrocarbons and in a preferred embodiment comprises C₂ to C₅ paraffins.General dehydrogenation process conditions include a pressure from about0 kPa(g) to about 3500 kPa(g); a reaction temperature from about 480° C.to about 760° C.; a liquid hourly space velocity from about 1 to about10 hr⁻¹; and a hydrogen/hydrocarbon mole ratio from about 0.1:1 to about10:1. Dehydrogenation conditions for C₄ to C₅ paraffin feeds may includea pressure from about 0 kPa(g) to about 500 kPa(g); a reactiontemperature from about 540° C. to about 705° C.; a hydrogen/hydrocarbonmole ratio from about 0.1:1 to about 2:1; and an LHSV of less than 4.Additional details of dehydrogenation processes and catalyst may befound for example in U.S. Pat. No. 4,430,517 and U.S. Pat. No.6,969,496.

Generally, the dehydrogenation catalyst comprises a platinum groupcomponent, an optional alkali metal component, and a porous inorganiccarrier material. The catalyst may also contain promoter metals and ahalogen component which improve the performance of the catalyst. In anembodiment, the porous carrier material is a refractory inorganic oxide.The porous carrier material may be an alumina with theta alumina being apreferred material. The platinum group includes palladium, rhodium,ruthenium, osmium and iridium and generally comprises from about 0.01 wt% to about 2 wt % of the final catalyst with the use of platinum beingpreferred. Potassium and lithium are preferred alkali metal componentscomprising from about 0.1 wt % to about 5 wt % of the final catalyst.The preferred promoter metal is tin in an amount such that the atomicratio of tin to platinum is between about 1:1 and about 6:1. A moredetailed description of the preparation of the carrier material and theaddition of the platinum component and the tin component to the carriermaterial may be obtained by reference to U.S. Pat. No. 3,745,112. Again,multiple reactors or reaction zones may be used to manage the heat ofreaction as described above for the reforming process. Thedehydrogenation process regeneration zone pressure may range from about0 kpa(g) to about 103 kPa(g).

1. A method for transferring particles from an upper zone, through amiddle zone, to a lower zone comprising: (a) introducing a first gasstream into the lower zone; (b) transferring particles downward from theupper zone to the middle zone through an upper valveless conduit, andtransferring gas from the lower zone upward through a lower valvelessconduit into the middle zone; (c) increasing the middle zone pressure;(d) transferring particles downward from the middle zone to the lowerzone through the lower valveless conduit, obstructing a particle flow inthe lower zone with a particle impervious body comprising a planarsurface, and transferring gas from the middle zone upward through theupper valveless conduit into the upper zone; and (e) decreasing themiddle zone pressure.
 2. The method of claim 1 further comprisingmaintaining an inventory of particles in the upper zone, and maintainingan inventory of particles in the lower zone.
 3. The method of claim 1further comprising sensing the level of particles in the middle zone,and transmitting a signal to initiate step (e).
 4. The method of claim 1wherein particles transferred to the lower zone are discharged from anoutlet of the lower valveless conduit towards the planar surface of theparticle impervious body.
 5. The method of claim 1 wherein particlestransferred to the lower zone are discharged from an outlet of the lowervalveless conduit, the outlet being located within the lower zone. 6.The method of claim 1 wherein the upper zone is at a first pressure, thelower zone is at a second pressure, and the second pressure is greaterthan the first pressure.
 7. The method of claim 1 wherein the pressurein the middle zone is greater than a pressure in the upper zone duringat least a portion of step (c).
 8. The method of claim 1 furthercomprising forming a continuous mass of particles comprising particlescontacting the planar surface of the particle impervious body, particleswithin the lower valveless conduit, and particles within the middlezone.
 9. The method of claim 8 wherein the continuous mass of particlesis formed during step (d).
 10. The method of claim 8 wherein thecontinuous mass of particles exists when step (e) is initiated.
 11. Themethod of claim 1 further comprising passing particles from the planarsurface of the particle impervious body to the volume of the lower zonebelow the planar surface.
 12. The method of claim 1 further comprisingintroducing a second gas stream to the middle zone to increase themiddle zone pressure in step (c) and venting gas from the middle zone tothe upper zone through the upper valveless conduit in step (e).
 13. Themethod of claim 1 further comprising transferring at least a portion ofgas from the lower zone to the middle zone through a first gas conduitto increase the middle zone pressure in step (c), and venting gas fromthe middle zone through a second gas conduit in step (e).
 14. The methodof claim 14 wherein the middle zone is vented through the second gasconduit to the upper zone in step (e).
 15. The method of claim 1 whereinduring step (c) the middle zone pressure is equilibrated with the lowerzone pressure, and during step (e) the middle zone pressure isequilibrated with the upper zone pressure.
 16. A method for transferringparticles from an upper zone, through a middle zone, to a lower zonecomprising: (a) introducing a first gas stream into the lower zone; (b)transferring particles downward from the upper zone to the middle zonethrough an upper valveless conduit, transferring gas from the middlezone to the upper zone through the upper valveless conduit, andtransferring gas from the lower zone upward through a lower valvelessconduit into the middle zone; (c) introducing a second gas stream to themiddle zone to increase the middle zone pressure; (d) transferringparticles downward from the middle zone to the lower zone through thelower valveless conduit, obstructing a particle flow in the lower zonewith a particle impervious body comprising a planar surface, andtransferring gas from the middle zone upward through the upper valvelessconduit into the upper zone; and (e) venting the middle zone to theupper zone through the upper valveless conduit to decrease the middlezone pressure.
 17. The method of claim 16 further comprising forming acontinuous mass of particles comprising particles contacting the planarsurface of the particle impervious body, particles within the lowervalveless conduit, and particles within the middle zone.
 18. A methodfor transferring particles from an upper zone, through a middle zone, toa lower zone comprising: (a) introducing a first gas stream into thelower zone; (b) transferring particles downward from the upper zone tothe middle zone through an upper valveless conduit, and transferring gasfrom the lower zone upward through a lower valveless conduit into themiddle zone; (c) transferring at least a portion of the gas from thelower zone to the middle zone through a first gas conduit to increasethe middle zone pressure; (d) transferring particles downward from themiddle zone to the lower zone through the lower valveless conduit,obstructing a particle flow in the lower zone with a particle imperviousbody comprising a planar surface, and transferring gas from the middlezone upward through the upper valveless conduit into the upper zone; and(e) venting the middle zone through a second gas conduit to decrease themiddle zone pressure.
 19. The method of claim 18 wherein the middle zoneis vented through the second gas conduit to the upper zone.
 20. Themethod of claim 18 further comprising forming a continuous mass ofparticles comprising particles contacting the planar surface of theparticle impervious body, particles within the lower valveless conduit,and particles within the middle zone.